1. Field of the Invention
The present invention relates to a display device and a driving method thereof, and particularly, to a display device with a built-in touch panel and a driving method thereof.
2. Discussion of the Related Art
Touch panels are a type of input device that is included in display devices such as liquid crystal display (LCD) devices, plasma display panels (PDPs), organic light emitting display device (OLED), and electrophoretic displays (EPDs), and enables a user to input information by directly touching a screen with a finger, a pen or the like while looking at the screen of the display device.
Particularly, the demand for display devices integrated with an in-cell touch screen, which include a plurality of built-in elements configuring the touch screen for slimming portable terminals such as smart phones and tablet personal computers (PCs), is recently increasing.
FIG. 1 is an exemplary diagram showing waveforms of various signals applied to a related art in-cell display device. FIG. 2 is an exemplary diagram illustrating a configuration of a panel applied to the related art in-cell display device.
In the related art in-cell display device, as shown in FIG. 1, an image display period D and a touch sensing period T are divided by a touch sync signal TSS.
During the image display period D, as shown in FIG. 1, a gate pulse is sequentially supplied to a plurality of gate lines GL1 to GLg, and a common voltage is supplied to a plurality of touch electrodes TE used as a common electrode. Data voltages are respectively supplied to a plurality of data lines DL.
During the touch sensing period T, a touch drive signal is supplied to the touch electrodes TE, and thus, a touch is sensed. In this case, as shown in FIG. 1, touch assistance signals which are the same as or mimics the touch drive signal are supplied to the gate lines GL1 to GLg and the data lines DL.
By using the above-described driving method, loads of the touch electrodes TE are reduced, and touch sensitivity is enhanced.
For example, during the touch sensing period T, the touch assistance signals having the same level and phase as those of the touch drive signal is supplied to the gate lines GL1 to GLg and the data lines DL, and thus, a parasitic capacitance is not generated between the touch electrodes and the gate lines GL1 to GLg and data lines DL. Accordingly, touch sensitivity is enhanced.
However, in a case where the above-described driving method is applied, a touch sensor disposed at an outer portion of the panel has a condition which differs from that of a touch sensor disposed inside the panel.
For example, in FIG. 2, seven touch electrodes disposed at a left outer portion of a panel 10, seven touch electrodes disposed at a right outer portion of the panel 10, eleven touch electrodes disposed at an upper outer portion of the panel 10, and eleven touch electrodes (hereinafter simply referred to as an edge touch electrode TE1) disposed at a lower outer portion of the panel 10 are not adjacent to another touch electrode in at least one of up, down, left, and right directions.
However, in FIG. 2, a touch electrode (hereinafter simply referred to as a center touch electrode TE2) disposed inside the panel 10 is adjacent to other touch electrodes in all directions.
Moreover, an arrangement structure of data lines and gate lines which affect the edge touch electrode TE1 differs from an arrangement structure of data lines and gate lines which affect the center touch electrode TE2.
Therefore, a touch drive signal supplied to the edge touch electrode TE1 has a characteristic different from that of a touch drive signal supplied to the center touch electrode TE2 even when the touch drive signal is supplied to the edge touch electrode TE1 during the touch sensing period T and the touch assistance signals corresponding to the touch drive signal are supplied to the data lines and the gate lines.
Particularly, various lines such as a common voltage supply line, a high voltage supply line, and an antistatic line are disposed outside the edge touch electrode TE1, namely, in a non-display area.
Therefore, a parasitic capacitance is generated between the lines and the edge touch electrode TE1 and affects a touch performance of the edge touch electrode TE1.
For this reason, in comparison with the center touch electrode TE2, a touch sensitivity and a characteristic of the edge touch electrode TE1 are reduced, and a touch sensing ability and a touch performance of a display device are affected.